The present invention relates in general to pipes, and more particularly, to corrugated metal pipes.
Corrugated metal pipe is used extensively in flood control, drainage and sewer systems because of its economic value, strength and durability. The pipe is usually fabricated in 20 foot and 24 foot sections; however sections in other lengths are available. Widely used pipe diameters may range from 6 to as much as 300 inches and typical wall thicknesses are 0.052 inches (18 gauge), 0.064 inches (16 gauge), 0.079 inches (14 gauge), 0.109 inches (12 gauge), 0.138 inches (10 gauge) and 0.168 inches (8 gauge).
Corrugated metal pipe derives most of its inherent strength from the corrugations formed into the metal sheets or plates at the time of fabrication. Helical corrugated pipe is a common type of corrugated pipe with helical corrugations, fabricated from corrugated metal sheet, with a continuous helical seam. Corrugated metal sheet is a mill product in sheet or coil form for fabricating helical corrugated pipe products. Corrugations commonly used for metal pipes are circular arcs connected by tangents, and are described by pitch and depth. Pitch is measured at right angles to the corrugations from crest (peak) to crest (peak) on a same side of a pipe sheet. Depth of a corrugation is measured from a crest of a corrugation to the lowest portion of an adjoining valley, both measured on a same side of a pipe sheet. A corrugation is named using its pitch and depth as “pitch by depth.”
A standard “3×1” helical corrugation profile features a 3 inch pitch and a 1 inch depth. Seven (7) corrugations are included on each side of the metal sheet. The corrugated metal sheet is formed from a flattened sheet having a width of about 27 inches (specifically 27¼ inches). The finished (corrugated) sheet width is 21″ (+−½ inch) with a lock seam. A standard “5×1” helical corrugation profile features a 5 inch pitch and a 1 inch depth. Six (6) corrugations are included on each side of the metal sheet. The corrugated metal sheet is formed from a flattened sheet width is about 34 inches (specifically 33 5/16 inches). The finished (corrugated) sheet width is 30″ (+−½ inch) with a lock seam. For large pipe diameters (over 48 inches), a 3×1 corrugation profile is the established industry profile. Traditional helical corrugated steel pipe (CSP) is limited to 144 inches in diameter to still meet the ASTM A796 Structural guidelines for horizontal deployment.
Due to the structural limitations of typical helical corrugated pipe, for larger diameter vertical and horizontal pipes (such as 168-300 inches) corrugated sectional steel plate is used. These larger corrugated metal pipes are typically used for vertical applications as caissons and foundations for shafts, and for horizontal pipe applications (such as in flood control, drainage and sewer systems). In this regard, a helical configuration is not used. Rather, individual sections of rectangular steel plate (of 120 inches by 72 inches) are each formed to have lengthwise corrugations and the metal plates are curved into widthwise arc segments. Multiple sections of metal plate are joined together to form sections of pipe. The periphery of the plate sections are punched to facilitate the plates being joined together. Typically, the steel plates are formed at a manufacturing plant and then shipped to the installation worksite. At the worksite, the curved sectional metal plates are delivered and then must be maneuvered to be assembled to form a pipe. This assembly process is a difficult process as the curved metal plates are cumbersome to maneuver by nature.
Accordingly, there exists a need in the art for an improved corrugated pipe arrangement in comparison to the prior art.